Researchers Miranda Giacomin and Nicholas Rule recruited participants to look at the faces of people who were all across the narcissistic spectrum, from a normal level to full blown narcissist — and it turned out they were pretty good at identifying them.

Strangely, when participants were shown pictures of just the eyebrows, they could correctly identify the narcissists too.

They highlighted femininity, grooming, and distinctiveness when they picked out the narcissists, but results showed it was distinctiveness that was key — narcissists tended to have darker, thicker, more distinctive eyebrows.

The researchers tested the results again by Photoshopping narcissists' brows onto the faces of non-narcissists, and vice versa, and the eyebrows gave the game away away again.

Eyebrows make our faces more recognisable, and in recent years they have become something of a fashion statement. Narcissists may like to make a statement with their brows so to tantalise potential love interests and make an impression.

As the authors wrote, they might "seek to maintain distinct eyebrows to facilitate others' ability to notice, recognise, and remember them; thereby increasing their likability and reinforcing their overly positive self-views."

It could also simply be because eyebrows give away more social messages than we realise. They are important for our facial expressions, but could also reveal subtle, subconscious information too.

"The ability to identify dark personality traits at zero-acquaintance provides particular value for avoiding exploitation and manipulation," the researchers wrote.

"The increasing incidence of narcissism underscores this value. Fortunately, people can accurately judge others' narcissism based on how they act, what they say, what they wear, and what their faces look like."

Whatever secrets eyebrows hold that mean they may reveal someone's dark personality, they could be reason enough to steer clear.